Woods have hitherto been used for various uses such as building materials, etc., because of the excellent features. However, woods are lacking in heat plasticity and are insufficient in dimensional stability, humidity resistance, mechanical properties, etc., according to the uses. From such a view point, it has recently been investigated to impart woods the functions such as thermo-plasticity which are not originally owned by woods by applying a proper chemical modification to the woods. These investigations are important from not only the development for new materials but also the point of effective utilization of unutilized woody sources, such as twiggy woods and periodically thinned woods, etc.
The inventors previously proposed a production process of modified wood chips by an oligoesterification of alternately adducting a dibasic acid anhydride and a monoepoxy compound to the hydroxy groups in the wood chips (Japanese Patent Publication (unexamined) No. 83806/85). Furthermore, it was found that the modified wood chips and the moldings obtained by heat-press molding these wood chips were excellent in humidity resistance and water restistance and also according to the kind of the oligoester chain, the wood components could be plasticized at the heat-press molding.
Thus, the inventors proceeded detailed investigations expecting that when an unsaturated double bond was introduced into the oligoester chain of the modified woody materials, crosslinking occured by the polymerization of the double bonds simultaneously with plasticization of the woody component of the oligoesterified woody material (hereinafter referred simply to the woody component) at the heat-press molding to provide cured woody moldings having more excellent performance. As the result of the investigations, it has been clarified that in the case of using a monoepoxy compound having unsaturated double bond as the raw material component for introducing unsaturated double bond into the oligoester chain, the oligoesterified woody material obtained can be plasticized only at high temperatures of higher than 180.degree. C., in particular, higher than 200.degree. C. and also the plasticizable extent is low. Furthermore, the tendency becomes remarkable with the increase of the content of woody components.
From the view point of the effective utilization of woody materials, it is very significant for industrial purposes to establish a production process of plasticized woody moldings having a large content of woody components. In regard to the molding temperature, if the molding temperature is not more than 180.degree. C., the moldings obtained are insufficient in homogeneity, mechanical strength, etc., since sufficient plasticization is not, as a matter of course, obtained, while if the molding temperature is over 180.degree. C., thermal decomposition of the woody material itself is caused even if plastization occurs and also such a high temperature condition is not preferably from the point of energy efficiency.